PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 6719842

Visual grouping without low spatial frequencies.

L Jáñez
View original source ↗Export metadata ↓

Abstract

Gestalt psychologists have stressed the perceptual importance of grouping. On the basis of multichannel theory of early visual processing, grouping has been attributed to the operation of channels tuned to low spatial frequencies. If this explanation is correct and sufficient, grouping should not occur when looking at highpass filtered images, because they do not excite low spatial frequency channels. However this paper brings evidence that visual grouping also occurs in such a situation. Hence, a more comprehensive explanation of visual grouping is needed.

Explore related subjects

FiltrationForm PerceptionHumansPattern Recognition, VisualPerceptual ClosureJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

L Jáñez. 1984. Visual grouping without low spatial frequencies.. https://doi.org/10.1016/0042-6989(84)90130-5

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1995

Research and development in the blood bank: efforts of a hospital donor center to improve efficiency of in-line leukocyte reduction filters for automated plateletpheresis.

In-line leukocyte reduction filters (LRF) are available for use with an automated plateletpheresis (PPH) system. Initially, 62% of PPH units produced with such a filter (LRF6, N = 29) had postfiltration (POF) white blood cell (WBC) counts < 5 x 10(6), with a mean POF WBC of 42 x 10(6). In an attempt to decrease POF WBCs, PPH were rested 30 to 60 minutes before filtration with LRF6. A new, larger-volume LRF (LRF10) was also assessed for its efficiency of leukodepletion. A total of 625 PPH, 490 filtered with LRF6 and 135 with LRF10, were evaluated using prefiltration (PRF) and POF samples. Mean prefiltration WBC loads averaged 80 x 10(6) (range, 60-88 x 10(6)) using seven combinations of filters, collection software, and PRF rest periods. Ninety-three percent of PPH units rested prior to filtration with LRF6 (N = 237) had < 5 x 10(6) WBC POF, with a mean of 5 x 10(6) WBC POF. All PPH units filtered with LRF10 (N = 135), whether rested or not, had < 5 x 10(6) WBC POF, with a mean WBC count of 0.2 x 10(6) POF. Mean platelet (PLT) yields POF ranged from 3.1 to 3.4 x 10(11). A PRF rest decreased mean POF WBC counts in products filtered with LRF6. The LRF10 consistently produced PPH with < 5 x 10(6) WBC POF. Blood centers must thoroughly validate equipment utilized in the production of blood components.

Filtration↗
PubMed1995

The effect of a heparin removal filter on platelet aggregation studies in heparin-induced thrombocytopenia.

Patients having a heparin-associated platelet antibody who are receiving heparin at the time of testing for heparin-induced thrombocytopenia (HIT) by platelet aggregometry may exhibit aggregation in the negative control channel. Filtering plasma to remove the heparin in may produce a nonaggregating negative control channel. The effect of the Pall Hepchek (Pall Biomedical, East Hills, NY) heparin removal filter on platelet aggregation studies was evaluated. Samples were studied from 10 patients with clinically established HIT. The pre-filtration platelet aggregation studies were unequivocally positive for heparin antibody. The remainder of each sample was filtered and the aggregation studies were repeated. Of the four patients on IV heparin, only one remained positive post-filtration. Of the six patients receiving subcutaneous heparin or flushes, one remained strongly positive, one was borderline, and four became negative. Pall Hepchek heparin filtration unpredictably alters the results of platelet aggregation studies, and should not be used routinely to remove heparin in the presence of aggregation in the negative control.

Filtration↗